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ZBasic Language Reference
99
ZX Microcontroller Family
The second method for guaranteeing atomicity of a sequence of one or more statements is to use the
System Library routines DisableInt() and EnableInt() in matched pairs as shown in the example
below.
Dim i as Integer
Sub Main()
Dim stat as Byte
stat = DisableInt()
i = 200
Call EnableInt(stat)
End Sub
The disadvantage of using this method is that the compiler does not attempt to verify that the disabling
and enabling are properly paired. Consequently, you might inadvertently omit the call to EnableInt()
which would prevent any further interrupts, effectively disabling serial I/O, the RTC, etc.
A third method of guaranteeing atomicity is to explicitly disable and re-enable interrupts as depicted
below.
Dim i as Integer
Sub Main()
Register.SREG = &H00
i = 200
Register.SREG = &H80
End Sub
Although this technique may be useful in rare cases, its use is strongly discouraged. The primary
problem with this method is that it unconditionally re-enables interrupts without regard to whether or not
interrupts were enabled beforehand. A related technique using inline assembly language code, having
the same disadvantage, is shown below.
Dim i as Integer
Sub Main()
#asm
cli
#endasm
i = 200
#asm
sei
#endasm
End Sub
4.5 Attributes for Procedures and Variables
This section describes several special attributes that you can apply to variables or procedures with native
mode devices to obtain special effects. To apply special attributes, you list the desired attributes (see the
table below) in a comma-separated list enclosed in parentheses following the keyword Attribute. This
entire construction is placed at the end of a normal variable, subroutine or function definition as illustrated
in the example below.
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